Deploy grading app interface improvements

Make Return on the login page submit Sign in instead of Register

Exclude test_user accounts from Stats Everyone and Other graders

Add a Stats dashboard and equal-width theme buttons

Align Go! right and dismiss all card-number errors after 5s

Fix card-number field sizing and non-digit Go! errors

Remove the Field of Law fail button from the grading app

Tidy short Q/A spread, fail-column gaps, and wrapping Other reason.

Align Back/Skip with the answer box and keep them on the right.

Align Pass/fail buttons in the content width and tidy the fail-reason sidebar

Restore fail-reason UI with markdown emphasis and hidden button tooltips

Render markdown emphasis in both grading boxes and hide button tooltips

Fix light-mode Other-reason placeholder and fail-reason help UI

Add fail-reason buttons with legend for grading UI

Render markdown bold in the grading definition box.

Polish grading login, toasts, and Material icons

Fix the grading progress bar so the fill tracks graded cards

Restyle grading card layout and save verdicts on Pass/Fail